I posted another thread on this issue but got limited responses. I have a JGC 4.0 Laredo and the electric fan has not worked for some time. I have replaced both of my relays in the PCM and the fan and the coolant temperature sensor but it still wont come on. The fan is non responsive not only to compressor activation but also to temperature. My vehicle does not have the relay that is sometimes situated under the headlight and I am wondering if there could be another cause?

Is the AC transducer module tied into temperature based activation as well as the compressor coming on? If so can this be removed from the line without discharging the system?

 

Seems you need a schematic and a volt meter. There must be a thermal switch that controls the fan. Also you could try hotwiring the fan to see if it comes on at all. Idk if the AC system has anything to do with it but highly doubt it.

 

You must be talking about an 02 or newer jeep. There is no thermal switch. The PCM reads engine temp and controls the fan relays itself. Normally the fan comes on high at 210* then drops to low at 195* and runs constantly until you shut off the engine, OR kicks back on high at 210* again. It will run on high anytime the A/C compressor is engaged.